Studies are being conducted on the ligand-induced oligomerization of the L-threonine dehydratase of Clostridium tetanomorphum, with particular attention being devoted to the effects of ADP, ATP and substrate analogues on the oligomeric state, as observed by equilibrium ultracentrifugation. Reaction kinetic data are also sought from several different types of assay to permit better correlation between molecular weight and enzymatic activity. The role of cyclic 3',5'-AMP in the synthesis of L-threonine dehydratase (degradative form) from Escherichia coli is under study. The enzyme is only formed in the presence of inducer (threonine) and in the absence of oxygen. The requirement for anaerobiosis appears to be related to the internal levels of cyclic AMP; the distinction to be investigated is whether the abnormally high cyclic AMP needed for induction is for messenger RNA synthesis or some other process. Other effort on this project is devoted to an examination of the properties of L-threonine dehydrasase of Pseudomonas putida. This enzyme appears to be involved in the synthesis of the alpha - ketobutyrate coenzyme of urocanase in the same organism. Of primary concern is the mechanism by which threonine dehydratase participates in coenzyme biosynthesis.